"The parasite’s life cycle is a really amazing strategy for an organism that doesn’t have a brain," says Byers, who predicts that anywhere gulls are prevalent, the C. lingua trematode would also be prevalent.
A laboratory experiment confirmed Wood’s and Byers?hypothesis: snails infected with the parasite ate 40 percent less macroalgae than uninfected snails. In the field, where researchers measured the macroalgae in three types of bottomless cages -- with no snails (control), uninfected snails, and infected snails -- they similarly saw less reduction of ephemeral algae by infected snails.
But when researchers isolated ephemeral, or edible, algae, "we saw dramatic change," says Byers. Edible algae account for a small proportion of macroalgae on rocky shorelines ?just about seven percent ?but they are an important food and habitat resource for a variety of organisms. Over the three-and-a-half-week field experiment, ephemeral algae increased 186 percent in the no-snails control cage and 59 percent in the cage of infected snails; it decreased by six percent in the uninfected snails treatment.
"Whatever controls that edible algae controls a lot," says Byers, noting that other snails, isopods, and possibly near-shore fish feed on ephemeral algae. "It’s suggestive that these non-lethal impacts of parasites have influential effects that can trickle down to affect other residents of the ecosystem."
Byers?and Wood’s study signals an increasing appreciation for parasites in e
Source:University of New Hampshire